Paraffin scraper



V oct. 25, 1949.

Filed March 20, 1945 G. MCCRAY ET AL.

PARAFFIN scRAER 2 Sheets-Sheet 1 Paren Agem Patented Oct. 25, 1949PARAFFIN SCRAPER George McCray and Ralph H.A Smith, Houston,

Tex., assignors to Stanolind Oil and Gas Company, Tulsa, Okla., acorporation of Delaware Application March 20, 1945, Serial No. 583,724

This invention relates generally to the removal of para'in from oil andgas wells, and in particular is directed to apparatus for paraffinremoval from the casing of wells producing uids through the annularspace between the tubing and the casing, such as wells producingseparately from each of two or more zones.

Various methods and devices have been proposed and used for removingparain from the production tubing of wells equipped in the conventionalway to produce from a single horizon. For example, solvents have beenintroduced into the tubing to dissolve and remove parain accumulationstherein in solution. However, due to the low solubility of the wax inmost of the available inexpensive solvents, comparatively large amountsof these are required, or more expensive and highly refined solventsmust be used.

Other systems of paraffin removal have relied upon liquefying the soliddeposits by the application of heat in some manner, such as byelectrical heating, circulation of steam, hot water, hot oil, combustiongases, and the like. While these systems are often satisfactory, specialequipment must 'ordinarily be provided for generating and transmittingthis heat energy into the well tubing.

The most used methods of paranin removal have been those in which theparafn is simply scraped or cut loose from the interior of the tubing bya tool passed through it. A large number of such mechanical cutters lorscrapers have been designed and used with satisfactory results for along time.

As long as the producing equipment of a well consists of a casing withinwhich is inserted a tubing for carrying all the production to thesurface, the Aparaffin deposits, if any, are confined chiefly to theinterior of this tubing, and can be satisfactorily dealt with by theforegoing removal methods. However, an increasing proportion of thewells now being drilled penetrate two or more separated productivezones, and many of these wells are being equipped to produce separatelyand simultaneously from each `of the Zones by utilizing both the tubingand the annular space between `it and the casing to conveythe fluidsseparately to the surface. This arrangement is commonly known as a dualcompletion." Also in certain Wells produced by gas lifting all of theproduction is taken through the annular space,r

8 Claims. (Cl. 166-18) tubing, which remains relatively clear ofaccumulations, but is mostly on the inner surface of the casing in theupper part of the well; Apparently the cooling of the paraffin-laden oilby heat loss through the casing to the comparatively cool earthformations in contact with the casing near the surface, combined withpossible cooling due to gas expansion, encourages this deposition tooccur, the inner casing Wall laording the necessary cool surface.

Due to the comparatively large Volume within this casing and to itsintimate contact with the surrounding earth, neither the solvent nor theheating methods of removal are as effective as when only a relativelysmall diameter tubing is to be cleaned. Excessively large volumes ofsolvent are required merely to fill this space, and when heating isattempted, large heat losses to the formations loutside the vcasinginevitably occur.

Since almost all wells deviate at least slightly from the vertical, thetubing is practically certain to lie close to or lcontact the casing atone or more points along its length. Due to this irregularity of theannular space the design |of a cutting or scraping tool that can beraised lor lowered through it presents apparent difliculties, with theresult that no such tool has been available. Consequently the procedureadopted for eld use heretofore has required that the well tubing becompletely removed from the Well before scraping tools are introduced.Ordinarily this means that heavy mud or other `control means must beernployed to shut off or kill the well production while the operationsare being perilormed. The interruption of the well production and thetime and expense of cleaning out the casing are correspondingly greatlyincreased, and the possibility exists of temporarily or permanentlyimpairing the well productivity if all of the heavy mud should not beremoved.

In view of this it is a primary object of our invention to provide animproved and practical apparatus for removing paraiiin deposits from theinterior of a well casing without removing the well tubing. Anotherobject is to provide equipment for mechanically cutting or scrapingparaffin from the lcasing of a dually completed or other well Whereproduction flows through the annular space, by the use of relativelylight and easily portable well pulling tools. A further object is toprovide such equipment in the form of a :permanent installation whichmay be left in the well, but whichdoes not impede Well productionthrough the annular space. A still further object is to provide forparaffin' removal from a well casing apparatus which can be employedwithout killing or shutting in the well for an extended period :of time,the only interruption necessary being only minor and temporary. Otherobjects, uses, and advantages of the invention will become apparent asthe description thereof proceeds.

In the drawings appended hereto and forming a part of this specificationwe have shlown an embodiment of our invention applied to a wellproducing from two separated zones. It is to be understood that thisembodiment is ilor purposes of illustration only, and that the noveltyof our invention is not to be considered as limited solely to theapparatus shlown. In these drawings, in which the same reference numeralin diiferent gures indicates the same or a corresponding part,

Figure 1 is a cross section of the upper end of an oil well showingipartly in elevation and partly in section typical surface equipment andpart of the apparatus of the invention;

Figure 2 is a cross section of the intermediate and lower parts of theWell with the remainder of the apparatus of the invention shown therein;

Figure 3 is an elevation with parts cut away showing the details of atelescoping or slip joint used in the invention; and

Figure 4 is an elevation, partially cut away, of a section of welltubing with a preferred type of cutting or scraping member attachedthereto.

Essentially, this invention comprises a plurality of paraffin-cuttingmembers attached to the tubing and spaced approximately uniformlythroughout the zone of paraiin deposition on the casing. At some pointin the tubing string below where the parafnn deposition starts isinstalled a telescoping or `slip joint which allows the upper part ofthe tubing string thereabove, carrying the cutting members, to be raisedand lowered a distance equal to or greater than the spacing betweencutting members. Thus by the simple operation of raising and loweringonly a part of the tubing string for a limited distance, which can bedone with easily portable and light weight pulling tools, the entireinner surface of the casing in that part of the well subject to parandeposition can be scraped and cleaned. Dislodged pieces of solidparaffin are carried out by producing the well atan appropriate rateduring the operations.

Referring now to Figures 1 and 2, a well I0 is shown drilled from theearths surface Il, equipped with a surface casing I2, an oil string ofcasing I3 extending through producing zones I4 and I5, and a productiontubing I6. Ordinarily a packer I1 is placed in the annular space betweenzones I4 and I5, and the casing I3 is perforated opposite both zones.With perforations in tubing I6 opposite only the lower Zone I5, it isapparent that production from each of the two zones is kept segregated.Production from zone I reaches the surface II via tubing I6 where it isdischarged into a flow line I8 controlled by a valve I9, while that fromzone I4 flows through the annular space between tubing I6 and casing I3,leaving the well through a iiow line 2!) controlled by a valve 2|.Master gate valve 22 may be provided to afford additional control -ofwell I0 As a safety measure a gate valve 23 and a blowout preventer 24are preferably installed just prior to carrying out the parain removaloperations. For lifting and lowering tubing string I6 a nipple 25 may beinserted through preventer 24 and valves v22 and 423, engaging threadsat the upper end of the top joint or section 26 of tubing I6. The upperend of joint 28 may suitably be of larger diameter than the rest of thejoint so as to provide a shoulder for supporting it and the rest oftubing string IS in tubinghead hanger 21. The outer surface of joint 26is preferably ground smooth and polished so as to slide easily through apacking 28 in hanger 21 without causing excessive wear to the packing.

Spaced at approximately equal intervals throughout the entire zone ofparailin deposition, such as at the couplings of tubing I6, are scrapingor cutting devices 29, 30, 3l, and 32. At some depth below the lowermostof these cutters, which should be well below the lowest occurrence ofparain deposits, .a telescoping or slip joint indicated generally at 34is incorporated in tubing string I6. Below slip joint 34 is alsoinserted in tubing I6 a removable tubing plug 35 for cutting off flowthrough the tubing temporarily during the operations. This plug 35 maybe any of the commercially available types, preferably one which may beinserted and withdrawn on a steel wire line, and should be equipped withan equalizing vave by which the pressure in the tubing therebelow can bereleased before the plug is withdrawn.

The details of construction of the slip joint 54 may be varied withinwide limits, that shown in Figure 3 possessing certain advantages foruse in the present invention. This joint may suitably comprise an innertubing 36 and an outer tubing 31 of somewhat larger inside diameter thanthe outer diameter of tubing 36, leaving a small annular space betweenthem. Threaded to the lower end of outer tubing 31 is a sleeve 38carrying a recess containing packing 39 compressed by a threaded nut 40.Packing 3S seals against the outer surface of inner tubing 36, which ispreferably ground smooth and polished.

Threaded to the upper end of inner tubing 36 is,

a tip 4I having a beveled face 42 adapted to seat against a shoulder 43at the upper end of outer tubing 31 when joint 34 is in closed position.

When seated, this prevents possible foreign matter from entering andclogging the space between tubes 36 and 31.

The outside of tip 4I is provided also with spurs or teeth 44, whichengage corresponding teeth 45 on the inside of sleeve 38. It will beapparent that when joint 34 is extended so that teeth 44 and 45 areengaged, as in the manner of a spline joint or jaw clutch, torque may betransmitted through joint 34 to that part of tubing IS below it for anydesired purpose, such as setting a packer, regulating a bottom holechoke, backing olf or unscrewing a left-hand threaded safety nipple, andthe like. As indicated previously, the lengths of tubes 36 and 31 mustbe suicient to permit a vertical movement of the upper part of tubing I6somewhat in excess of the spacing between the cutters xed to it.

A variety of types of paraffin scraping or cutting members may bedevised, bearing in mind the limitation that flow through the annularspace must not be unduly impeded. The scraper shown in Figure 4 has beentried and found practical. Secured to and projecting radially from asleeve 46 are a large number of spring wire iingers 41, of a lengthsufficient to contact casing I3 simultaneously at points around itsentire circumference. If desired, the ends of each of the wire fingers41 may be flattened so as to present a sharp knife-like edge to theparaiin deposits.

In Figure 4 is shown also a preferred manner vof securing these scrapingdevices to the tubing I6. The inside diameter of sleeve `46 beingslightly larger than the outside diameter of the'upset `portion 48 oftubing I6 near each tubing coupling, sleeve 46 is accordingly slippedover upset .48, thin metal shims being inserted between if .necessary tomake a tight fit. Thereafter sleeve 46 is tack welded to upset 48 at twoor more places, such as at 49 and 50.

In operation, after the insertion ofv plug 35 to shut off the flowthrough tubing I6 and the installation of valve 23 and blowout preventer24, lifting nipple 25 is coupled to the upper. end of tubing joint 26.Then by means of a hoisting or pulling unit, of which only the tubingelevator 5I is shown, that part of the tubing I6 above slip joint 34 isslowly raised and lowered while the -well is being produced through theannular space .to sweep out the dislodged parain. By noting any decreasein tension required to raise the upper enclV of tubing I6 and byexamining the oil flowing in line for the presence of paraffin cuttings,an estimate can be made of when the casinghas been suiiiciently cleaned.The cutting ac- .tion is improved if tubing I6 is rotated slowlyyposition was occurring on the top 1500 feet of casing. The telescopingor slip joint assembly -34 in this well was installed at a depth ofabout 3000 feet, the total length of the tubing being labout 10,000feet. This joint 34 allowed about a 28-foot vertical movement of the top3000 feet of tubing, and the individual cutters were installed atapproximately .Z5-foot intervals, beginning slightly more than feetbelow the tubing hanger and extending about 100 feet below the lowestknown parain deposits. Using a light weight pulling unit, and adjustingthe production through the annular space to about 12 or 15 barrels perhour, it was found that raising and lowering the apparatus about 1'7times at 90-day intervals kept the casing satisfactorily free of eX-cessive parain. The total time to perform each entire cleaning operationaveraged only about six hours, representing a very great saving in time.Naturally the time interval between successive cleanings will varywidely from well to well, and the details and dimensions of the variousparts of the apparatus can be modified to suit particular wellconditions. For example, if three or more formations are producedthrough concentric tubing strings, and deposition is found to beoccurring on one of the outer strings, the next adjacent inner stringcan be equipped with Scrapers and a slip joint as taught herein, for thepurpose of removing the deposits.

It will be apparent also that in wells where the lower end of the tubingis free to move, as where the well fluids are being gas lifted throughthe annular space and there is no packer, cleaning of the inner casingwall may be satisfactorily done by omitting the sliding joint and usingonly the plurality of Scrapers on the tubing. As in such an installationthe entire tubing string must be lifted and lowered, heavier hoistingequipment 'may be required, but one of the principal advanvby the scopeof the appended claims.

We claim:

1. In a cased dual-completion well structure, adapted for recovery ofhydrocarbon products from a, plurality of spaced producing strata, atubular producing conduit extending within and spaced from the wellcasing, thereby providing an inner producing conduit and an outerproducing conduit within the well, the outer conduit having spaced fluidinlets, theinner conduit having a fluid inlet adjacent its lower end, afluid-excluding seal between said conduits and between the spaced fluidinlets of the outer conduit and above the fluid inlet of the innerconduit, said seal preventing fluid flow between said conduits, atelescoping, fiuid-tight joint in said tubular conduit,

a plurality of spaced parain-cutting members fixed to the exterior wallof said tubular conduit above said joint, and means for reciprocatingthe portion of said tubular conduit above said joint.

2. In a cased dual-completion well structure, adapted for recovery ofhydrocarbon products from a plurality of spaced producing strata, atubular producing conduit extending within and spaced from the wellcasing, thereby providing an inner producing conduit and an outerproducing conduit within the well, the outer conduit having vspacedfluid inlets, the inner conduit having a fluid inlet adjacent its lowerend, a fluid-excluding seal between said conduits and between the spacedfluid` inlets of the outer conduit and above the fluid inlet of theinner conduit, said seal preventing fluid ow between said conduits, atelescoping, fluid-tight joint in said tubular conduit, a plurality ofspaced paraffin-cutting members fixed to the exterior wall of saidtubular conduit above said joint, the spacing between said members beingless than the telescoping movement of said joint, and means forreciprocating the portion of said tubular conduit above said joint.

3. In a cased dual-completion well structure,

adapted for recovery of hydrocarbon products 50y from a plurality ofspaced producing strata, a tubular producing conduit extending withinand spaced from the well casing, thereby providing an inner producingconduit and an outer producing conduit within the well, the outerconduit having spaced fluid inlets, the inner conduit having a iiuidinlet adjacent its lower end, a uidexcluding seal between said conduitsand between the spaced fluid inlets of the outer conduit and above thefluid inlet of the inner conduit, said seal preventing fluid flowbetween said conduits, a telescoping, fiuid-tight joint in said tubularconduit and a plurality of spaced paraffin-cutting members fixed to theexterior wall of said tubular conduit above said joint, 'said joint andthe lowermost of said spaced members being disposed at points on saidtubular conduit below the point at which paraffin deposits in theconduit formed between the outer surface of said tubular conduit and theinner surface of said casing.

4. In a cased dual-completion well structure, adapted for recovery ofhydrocarbon products from a plurality of spaced producing strata, atubular producing conduit extending within and spaced from the wellcasing, thereby providing an inner producing conduit and an outerproducing 7 conduit within-the well, the cuter conduit having `spacediiuid inlets, the inner conduit having a fluid inlet adjacent its lowerend, a iluid-excluding sealbetween said -conduits and between the spaceduid inlets of the outer conduit and above the fluid inlet of the innerconduit, said seal preventing fluid flow between said conduits, atelescoping, fluid-tight joint in said tubular conduit and a pluralityof spaced paraffin-cutting members xed to the exterior wall .of saidtubular conduit above said joint, said paraffin-cutting memberscomprising a plurality `of flexible elements with intersticestherebetween, and means for reciprocating the portion of said tubularconduit above said joint.

`5. In a cased dual-completion well structure, adapted for recovery ofhydrocarbon products from a plurality of spaced producing strata, atubular producing conduit extending within and spaced from the wellcasing, thereby providing an inner producing conduit and an outerproducing conduit within the well, the outer conduit having spaced iiuidinlets, the inner conduit having a fluid inlet adjacent its lower end, afluidexcluding seal between said conduits and between the spaced fluidinlets of the outer conduit and above the fluid inlet of the innerconduit, said seal preventing fluid flow between said conduits, atelescoping, fluid-tight joint in said tubular conduit and a plurality-of spaced paraffin-cutting members fixed tothe exterior wall of saidtubular conduit above said joint, said paraffin-cutting memberscomprising a plurality of radially disposed wires the .outer ends ofwhich contact the inner surface of said casing, and means forreciprocating the portion of said tubular conduit above said joint- 6.In a cased vdual-completion well structure, adapted for recovery ofhydrocarbon products from a plurality of spaced producing strata, atubular producing conduit extending within and spaced from the wellcasing, thereby providing an inner producing conduit and an outerproducing conduit within the well, the outer conduit having spaced iuidinlets, the inner conduit having a fluid inlet adjacent its lower end, afluidexcluding seal between said conduits and between the spaced fluidinlets of the outer conduit and above the fluid inlet of the innerconduit, said seal preventing fluid flow between said conduits, atelescoping, fluid-tight joint in said tubular conduit and a pluralityof spaced parailln-cutting members fixed to the exterior wall of saidtubular conduit above said joint, stops at either end of `saidtelescoping joint to limit the vertical movement of said tubular conduitabove said joint while permitting vertical movement for a distancegreater than the spacing between said parain-removing members, and meansfor reciprocating the portion of said tubular conduit above said joint.

7. In a cased dual-completion well structure, adapted .for recovery ofhydrocarbon products from a plurality of spaced producing strata, atubular producing conduit extending within and spaced from the wellcasing, thereby 'providing an inner producing conduit and an outerproducing conduit within the well, the Aouter conduit having spacedfluid inlets, `the inner conduit having a fluid inlet adjacent its lowerend, a fluid-excluding seal -between said conduits and between thespaced Iluid inlets of the outer conduit and above the fluid inlet ofthe inner conduit, said seal 'preventing fluid flow between saidconduits, a telescoping, fluid-tight joint in said tubular conduit andaplurality of spaced paraffin-cutting membersxed to the exterior wall ofsaid tubular conduit above said joint, a clutch built into saidtelescoping joint whereby the portion of said tubular conduit below saidjoint 'may be rotated ,around its major axis responsive to similarrotation of the portion of said tubular conduit above said joint, andm-eans for reciprocating the portion fof said tubular conduit above saidjoint.

8. In a cased :dual-completion well structure, adapted for .recovery ofhydrocarbon products from a plurality of spaced Aproducing strata, anouter casing in said well, said outer casing hav ing spaced fluidinlets, :an inner producing tubular conduit within said casing andspaced therefrom, said inner tubular conduit comprising a tubular uppersection, a tubular lower section and a telescopin-g, fluid-'tight `jointconnecting said upper and lower sections, said lower section having afluid inlet adjacent its lower end, a fluid-excluding seal between saidcasing and said lower section and ybetween the spaced uid inlets of saidcasing and the fluid inlet of said lower section, said lseal preventingfluid .ow between the channels formed by said casing and said innerconduit respectively, za plurality of .spaced paraiiin-cutting membersailixed vto said upper section, means for vertically reciprocating androtating said upper section independently of said lower section toremove paraln from ythe inner surface of said casing, above said joint,without shutting oif well production.

y'GEORGE MCCRAY. RALPH H. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,342,618 Bashara June 8, 19201,806,073 MacGregor et al. May 19, 1931 1,919,350 Wickersham July '25,1933 2,074,608 Gosline Mar. 23, 1937 2,304,303 Ferguson Dec. 8, 19422,315,931 Burt et al. Apr. 6, 1943 2,341,832 Verheul et al Feb. 15, 19442,374,317 Wright Apr. 24, 1945

